corwin1968

I'm going to post this here because we have a 55 page thread on drop-bar conversions so I know a lot of folks here have done it.

When you switch from an MTB bar to a drop-bar, do you keep the same length stem, get a shorter stem or get a longer stem? I know road bikes generally have a shorter top-tube and using the hoods extends your reach significantly so getting a shorter stem seems to make sense but I would like to hear the experiences of people who have actually done it.

jimmuller 

I've never done the switch you ask about, but I've done the reverse. I swapped stem too to move the bar closer and higher. Had good reasons for that.

The thing is, riding position is so different that it probably isn't a simple question. Your hand positions are very different, your posture on the bike is different, you balance differently, apply power differently, etc. Bar height can be traded off with forward reach; a shorter reach pulls your hands in and lets you drop the bar for more vertical arms. You can ride on the tops easily, or on the hoods, or on the bend in the bar behind the levers, or on the drops themselves. Your palms are rotated inward for all positions except the tops. This lets your elbows bend differently. So many differences.

Aemmer

If your goal is to build a true C/V bike emulating the original dirt drop Mtb's from the 80's then the idea is to get the drops in the same level and reach you would have on the bike with your flat or raised bar bitd.

Think very tall ( Salsa P7, P10, Nitto Dirt drop, LD) and short.

Unlike a road bike, the primary place for your hands should be in the hooks like here:



Crappy pic but. See how the brake and shifter are right there ready to use without removing hand from drops. rider gets the added suspension from the bar design and a comfortable hand position.

Edit , initial test ride so yes cable was still long.

corwin1968

Actually, it's not even a vintage bike but rather a brand new frame. I couldn't decide where to post but the 55 page on drop bar conversions led to me posting here.

My frame is an all-rounder and has a 55cm seat-tube and a 55.4cm top-tube, which to me is on the shorter side of things compared to what I've been riding. A 17 degree 110mm stem gets my mtb bar in the same position as my old bike but I also plan to do a drop-bar conversion in the future and I'm trying to get a rough idea of where to put the drop bar so I can run the numbers thru some fit programs and figure out how long to leave the steerer tube.

striknein

For a road-going MTB conversion, your frame's geometry will make a big difference too. Most vintage mountain bikes have a horizontal top tube and short head tube, so the stem necessarily needs to be taller than a road bike to allow for a comfortable riding position. You're also dealing with a longer top tube than a road bike, so you may not need as much reach.

Finding a road bike that fits is something of a challenge for me, having short legs and a long torso. If the bike's head tube is fairly steep, I can get away with using a road stem (80-100mm reach). But if the head tube is more slack (like my 83 Stumpjumper), a shorter stem allows me to compensate for steering that would otherwise be a bit sluggish.

wrk101

I need to take a side by side pic with my drop bar conversion vs my road bike. In the case of both of my conversions, I was able to use the original stock stem. MTB frame size was a full 2 inches smaller than my road bike size, but over an inch larger than my mtb size.

All of this is with a vintage bike.

The point, at least to me, was to make a suitable drop bar bike at a minimal investment. When you do a parts bin build, its easy enough to swap the stem if you aren't happy with it.

+1 I have short legs, long torso.

Notice not that much seat post showing. Higher bb negates much of the difference in frame size.

illwafer

just do it. leave your cables long until you hone in your fit. you may not want the same exact fit as your road bikes, so just keep an open mind.

himespau 

Sizing down a size or two on the mtb and having a lot of seatpost showing will allow you to have the same length stem (assuming you can find a really tall one like the nitto technomic and get that to work for you).

Velognome 

I kept the original stem and swapped out the bars. It's a long reach to the hoods, at first it feels too long, then I don't notice it anymore until I switch to a road bike and then that fees so short until I get used to that and I switch agian it begins all over again. Sometimes it's nice to change things up a bit.

anixi

+1 as above, did as Velognome did. And, as with Bill, my legs are short and my torso long. I just found that the seat tube had to be the same c-t as my road bike, 23.5". I was very lucky to find it to replace the 22" one that it replaces. Also, I just used the steel stem that came with the bike, a Giant Rincon and it works just perfectly for what I need.

It's so tall that I find gravel grinding a little sketchy, but, the riding position is perfect. I've also only done one gravel grinding session with it so far. I'm sure I'll get more confident since I've been a mountain biker for over 15 years.

Anyways, I don't know if it's a long torso thing or not, but no matter, you should try to find a frame that's within an inch or so of your road bike, IMO.

ThermionicScott 

In my case, I needed some trial-and-error to dial in my fit. The MTB has the same top tube length as my road bikes, but the slacker angles necessitated more reach. The stock MTB quill stem has the equivalent of 100mm extension, which was nice since I preferred 80mm on the road bikes. In the end, I bought Velo-Orange "Rando" bars to get the most reach while in the drops. Almost perfect now.

Velognome 

In the old days, 1920's, the frames had very slack angles and they used a forward extension seat post to get the rider over the pedals and effectively reduced the reach. like so:


From collectvelo's flicker site

I measured my 1989 Giant Iguana against a 1917 frame in my collection and bingo! Same tube lenghts and angles. So maybe a forward set seat post has more advantages then a shorter stem? I've been thinking about that lately, may just flip a set-back post around and see how she rides

ThermionicScott 

Good point, and a great illustration. One of yours?

I think it depends on where the movement needs to occur. For a bike like my '88 Diamondback, scootching the saddle forward a little gets the job done, but an older bike with 68-degree angles (or less!) would almost require one of those old-school seatposts.

Yo Spiff

I kept the same stem, but did a couple of handlebar swaps to get the hood where I liked them. I already had a very short reach stem on the bike, so another stem would not have been an option for me.